The subject of the present invention is a safety syringe for medical use.
A syringe comprises a tubular body made of glass or a synthetic substance, intended to contain the liquid that is to be injected, one end of which is equipped with an injection needle, and inside which is fitted a plunger seal that can be actuated by a stem protruding from the body at the opposite end to the end equipped with the needle. Prior to use, the needle is generally covered by a protective element, for example made of rubber. Once the liquid contained in the body of the syringe has been injected, by actuating the plunger using the stem, the needle remains bare, and this represents a risk of stick injury, which carries the risk of the transmission of certain diseases, such as hepatitis or AIDS.
As the selling price of a conventional syringe is very low, the invention aims to provide a safety syringe, the selling price of which is increased only a small amount by comparison with that of a conventional syringe, and which has a needle-protecting device which automatically covers this needle in the same movement as the injection movement so as to protect the needle after injection without the need for an additional and deliberate handling operation on the part of the user.
To this end, in the syringe to which it relates, which is of the aforementioned type, the syringe body is equipped, at its rear end, with at least one radial tab, a tubular piece of a length at least equal to the length of the syringe body increased by the length of the needle and having at least one axial slot extending from its rear end, each slot serving for the passage of one radial tab, this tubular piece being mounted so that it can slide along the body, and the stem of the plunger seal is equipped with means for axial immobilization inside the tubular piece, with this immobilization being freed at the end of the travel of the plunger seal, so as to allow the tubular piece to continue its axial movement, so that the front end of this tubular piece sheathes the needle.
Advantageously, the syringe body is equipped at its rear end with a sleeve secured to the body and coaxial therewith, to which it is connected directly or indirectly by at least one radial tab.
Prior to injection, the stem of the syringe and the tubular piece are secured one to the other. To carry out injection, the operator exerts pressure on the tubular piece. At the end of injection, the tubular piece detaches from the plunger stem and continues its forward movement, its front part then sheathing the needle, thus avoiding any risk of stick injury on this needle.
According to a first embodiment of this syringe, the means for axially immobilizing the stem of the plunger seal inside the tubular piece consist of flexible tabs secured to the end of the stem and extending the latter, these tabs facing from the inside outwards, and of which the free ends, which form a collar with a rib or a groove, collaborate respectively with a groove or annular rib formed on the inside of the tubular piece at a distance away from the rear end thereof which is at least equal to the length of the needle. At the end of injection, the tabs arranged at the rear end of the plunger stem engage in the body of the syringe, which moves the tabs closer together and allows them to detach from the tubular piece, which can thus continue its forward movement.
According to another embodiment, the means for axially immobilizing the stem of the plunger seal inside the tubular piece consist of a collar formed at the rear end of the stem of the plunger seal and projecting radially outwards, this collar being deformable by virtue of the presence of at least one axial slot open at the rear of the stem, this collar having a chamfered end edge and being intended to be engaged in an annular groove formed on the inside of the tubular piece at a distance away from the rear end thereof which is at least equal to the length of the needle.
In this case, at the end of the forward travel of the plunger, the stem is immobilized, and continued pressure exerted on the tubular piece allows the latter to detach from the rear end of the stem, given the flexibility afforded by the structure thereof.
Advantageously, the rear end of the tubular piece is closed by a cap which makes it more rigid.
The additional rigidity thus afforded is important, particularly in preventing undesired detachment between the rear end of the stem and the tubular piece.
To make the syringe easier to handle, the sleeve comprises, near its rear end, a complete or partial collar which projects outwards.
According to one possibility, the sleeve forms an integral part of the body of the syringe and is obtained by moulding a synthetic material at the same time as this body.
According to another possibility, the sleeve, produced independently of the syringe body, is secured to a bush of an inside diameter matched to the outside diameter of the syringe body.
According to one embodiment of this syringe, the tubular piece comprises, at its front end, a frangible extension intended to sheathe the needle before the syringe is used.
Before the syringe is used, the frangible extension may be separated from the tubular piece, for example by a twisting movement.
The tubular piece is short enough that, before injection, the front end of the body of the syringe is visible so as, for example, to allow the clarity of the liquid to be injected to be checked.